Understanding Batteries

How Batteries Are Rated

There are a few key factors to know when purchasing a battery.

Amp Hour Capacity: This is the measure of how much energy a battery can store. This is often listed as a C20 rate, which means this is the total energy capacity of the battery when charged or discharged steadily for 20 hours. It is also good to know that some batteries are listed at C100 (100 hours) or C6 (6 hours) which can be confusing. When comparing batteries be sure that you are comparing the same C rating.

Number of Cycles at Depth of Discharge: The next key factor when comparing batteries is seeing how many times you can cycle a battery to what depth. In all flooded lead acid batteries, the more deeply you discharge them, the fewer cycles they will have. Many lead acid batteries will have the longest life if only cycled down to 70% state of charge (SOC). This means that out of a 100 Amp Hour battery you really only have 30 Amp “usable Amp Hours” to achieve a long life from that battery. Many of the larger industrial batteries are designed to be cycled much more deeply, some as deep as 20% SOC. Using the same theoretical 100 Amp Hour battery, this means that you have 80 usable Amp Hours.

Voltage: Flooded cells have about 2VDC output potential, this difference is how they are connected to achieve a desired voltage. Common automotive batteries have 6 cells to provide a 12 VDC power supply. Very common in the renewable energy world are battery models such as the L-16 or “golf cart” battery. These are batteries with 3 cells that provide a steady 6 VDC power supply that can be series connected together to provide 12, 24, or 48 VDC power for home or business stand-alone (off grid) or battery backup inverters. Larger industrial sized batteries are often comprised of large Individual 2VDC cells either on their own or built into cases. These batteries are designed for larger off grid systems such as micro grids or systems that require large amounts of stored energy.

The Different Types of Batteries

Flooded lead acid (Flooded):The industry standard for renewable energy systems, flooded lead acid batteries (sometimes called just flooded) are bang for buck the cheapest most reliable source of energy storage out there. Using sulfuric acid and lead plates (sounds toxic but also fully recyclable) encased in a plastic casing, these batteries come in many different shapes and sizes. A typical flooded battery is made up of cells each with the electrical potential of about 2 VDC.Built into many different configurations, flooded batteries range from 6 celled 12 VDC automotive types to massive industrial 2VDC batteries.

Cons:Low energy density (heavy, not a great choice for mobile applications), potential exposure to hazardous materials (lead, sulfuric acid), decreased storage capacity when drained too deeply or left to sit with a low state of charge, regular maintenance required (adding distilled water, cleaning and tightening terminals).

Gel, AGM (absorbed glass mat), VRLA (valve regulated lead acid): Very similar to the flooded lead acid battery in size and chemistry, the gel or glass matt batteries differ in that the electrolyte (in this case acid) is either in gel form or absorbed in a fiberglass matting. Doing this removes the need for regularly adding distilled water, so they are often called maintenance free lead acid batteries.

Pros: Little to no maintenance (great for hard to service applications), easy to transport and ship (without exposure to acid spills), long reliable reliable service life.

Lithium Ion (Li-Po): The cutting edge of battery technology and most common battery for use in mobile applications (electric cars, laptops, phones, power tools, etc.), they are now beginning to find their way into home or business renewable energy operations. They have a tremendous life expectancy and no memory from over discharging or incomplete charging. With a number of new manufacturers hitting the market we hope to see these batteries take over for the lead acid series soon. At present,the cost is often a bit too high for the storage capacity needed for many renewable energy systems.

Pros: Superb life expectancy regardless of depth of discharge, high energy density (light for their capacity), no maintenance or upkeep.

Cons: Very particular charging parameters, cost per amp hour storage

Shipping Notes:

Some batteries are not available for standard freight shipping. For all battery sales please see shipping notes that apply.